Over the years a variety of material dispensers have been developed including those directed at dispensing foamable material such as polyurethane foam which involves mixing certain chemicals together to form a polymeric product while at the same time generating gases such as carbon dioxide and water vapor. If those chemicals are selected so that they harden following the generation of the carbon dioxide and water vapor, they can be used to form “hardened” (e.g., a cushionable quality in a proper fully expanded state) polymer foams in which the mechanical foaming action is caused by the gaseous carbon dioxide and water vapor leaving the mixture.
In particular techniques, synthetic foams such as polyurethane foam are formed from liquid organic resins and polyisocyanates in a mixing chamber (e.g., a liquid form of isocyanate, which is often referenced in the industry as chemical “A”, and a multi-component liquid blend called polyurethane resin, which is often referenced in the industry as chemical “B”). The mixture can be dispensed into a receptacle, such as a package or a foam-in-place bag (see e.g., U.S. Pat. Nos. 4,674,268, 4,800,708 and 4,854,109), where it reacts to form a polyurethane foam.
The above noted U.S. Pat. No. 4,800,708, which is incorporated herein by reference for background purposes, describes a method and apparatus for successively forming foam filled bags or cushions of the type wherein a foamable composition is deposited in a plastic bag. The formed bags are adapted to be placed in containers with articles being packaged, and so that when the foam expands, the bags and resulting foam are conformed to the configuration of the articles. The method and apparatus includes advancing a pair of plastic webs through the nip of a pair of drive rollers, while heat sealing the opposing longitudinal side edges of the webs together. Periodically, a predetermined amount of the foamable composition is deposited between the advancing webs immediately above the nip, and the heat sealing along the side edges is periodically and momentarily interrupted to form side edge openings for the subsequent escapement of gases generated during foaming. The advance of the webs is momentarily terminated, and a heated wire then engages the webs to sever the formed bag, while forming a sealed top edge of the formed bag and a sealed bottom edge for the next succeeding bag. The advance then again commences, and the cycle is repeated to successively form the foam filled bags.
As an example of a foam-in-bag dispensing system with a film feed for bag formation and chemical dispensing system reference is made to PCT/US2004/014423 filed on 7 May 2004 in the name of IntelliPack of Tulsa, Okla., US, and published in English as WO 2004/101252 A2, which PCT application is incorporated herein by reference. This reference uses a preferred “C-fold” film technique rather than the advanced webs from two different sources system utilized in U.S. Pat. No. 4,800,708.
U.S. Pat. No. 5,335,483 illustrates an additional foam-in-bag system featuring a C-fold film feed arrangement and with an adhesive strip seal formed on the free edges opposite the C-fold. As shown in FIG. 3 there is a blade device placed in contact with the C-fold film feed as it travels downstream from a guide bar. U.S. Pat. Nos. 4,854,109 and 4,999,975 illustrate additional foam-in-bag venting systems. An additional venting system is seen in U.S. Pat. No. 6,472,638 (see, for example, FIGS. 40 to 44) featuring a card inserts which include a vent formation heating wire
Some difficulties experienced with the prior art venting designs include inadequate vent formation and the potential for foam shrinkage and poor in-bag foam flow within the bag due to inadequate venting or over extended vent formation and the associated leakage potential (e.g., a failure to properly control the required temperature differential to differentiate between a seal and vent region during interruption of an edge seal for venting purposes causing either too small or too large a seal interruption). The interruption technique (such as the feathering of the flow of electrical current to a sealing heat wire or the movement of heat sealing equipment into and out of position) also can introduce undesirable added complexities associated with temperature or equipment controlling particularly in an environment where devices can become coated with foam, worn out or moved in position during use (e.g., melting into a support component). An additional problem with some prior art is that cut venting is often done on only the front or the back sheet which limits the venting capability. There is also associated with prior art devices difficulty in repair and replacement for a defective venting component due to for example, difficulty in accessing or difficulty in removing and proper replacement.